I wouldn't exactly call 28 inches per hours, "rocket charged"... maybe nano-rocket charged....now we can roll out those medical nano-bots to unclog the arteries of the US population, rather then get them on the treadmills!!

what is hydrazine?
why wasnt it used before on regular platinum, H2O2 fueled rocket motors?

Hydrazine is a very flammable material, it ignites when other material will not. Air forces use it on their planes, I don't know the extent, but hydrazine is usually used to get the main engines going. You are right the main engines on the ship use hydrogen, but to help it ignite for the first time, I am pretty sure they mix it with hydrazine. That is the same thing they did with the SR-71 Black Bird (fastest plane in the world), it uses fuel that is very hard to ignite (this plane would leak fuel while on ground and routine maintenance was performed) so the plane caries hydrazine to give that initial flame so that the afterburners could be ignited. That is why the SR-71 could only ignite the afterburners about 4 or 5 times while in flight. I am sure it is used for a similar purpose in the shuttle. By the way, from what I heard, unburned hydrazine is very dangerous chemical and if it starts to leak it will turn into gas and you better not breathe that stuff, or else you are a goner. The good thing is that it is so easily flammable that most times when it leaks it just burns itself out.